This invention relates to processing of ingots from pouring into molds through attainment of a ready-to-roll condition by a method which provides minimum energy requirements, minimum residence time in a soaking pit, improved yield and improved metallurgical quality. A mathematical model of the thermal behavior of ingots may be used to monitor the removal of ingots from molds ("stripping") and charging of ingots into a soaking pit, which may be combined with information from the soaking pit and knowledge of proposed rolling requirements, in order to control the operation of the soaking pit. The principal objectives of the process of the invention include:
retention of a specified amount of residual heat in rimming and semi-killed steel ingots throughout the soaking stage;
utilization of information on ingot strip time and charge time (to the soaking pit) and information from the soaking pit to determine if and the time at which to start heating or "firing" the soaking pit in such a manner as to provide minimum residence time in the soaking pit; PA1 avoidance of metallurgical problems incident to slow solidification times; and PA1 "Minimization of Fuel Consumption In Soaking Pits Using a Cylindrical Equivalent Model . . . ", J. R. Cook et al, AIME, Mar. 28-31, 1982, pp. 122-133; and PA1 "Liquid Centre And Hot Centre Rolling of Ingots Using On-Line Computer Control", J. R. Cook et al, ISA, Oct. 18-21, 1982, pp. 235-249. PA1 "Development of a Computerized System for Predicting the Progress of Soaking in a Soaking Pit", M. Hinami et al, The Sumitomo Search, No. 13, May 1975, pp 1-7; PA1 "Spherical Ingot Model and its Application to Control of Soaking Pit", E. J. Longwell et al, PLAIC Report 76, 1976; and PA1 "On the Rolling of Rimmed Steel Ingots in an Unsolidified State", J. Nogaki et al, Sumitomo Metal Ind. Ltd., 1980.
utilization of information from soaking and reheating stages to update the projection of ready-to-roll condition if conditions change in the soaking pit and to modify soaking pit operations to meet changes in pacing conditions in the slab rolling mill.
The above objectives require a definition of the ready-to-roll condition in terms of percentage of the ingot solidified and thermal gradient or profile through the ingot, for various grades of steel and ingot sizes.
The stripping of ingots and charging thereof to a soaking pit before complete solidification is disclosed in published Japanese application Nos. J 53134-756, J 55130-301, J 56009-005 and J 82052-937.
Background information relating to the present invention is described in the following articles jointly authored by the present inventors:
A publication by Process Control & Automation Inc., Technical Report No. 82-009-1, entitled "CEM.TM. Cylindrical Equivalent Model", deals with processing features of the present invention.
Other articles are referenced in the above-mentioned Cook et al articles, including: